A tumor suppressor locus in familial and sporadic chordoma maps to 1p36.

Previous cytogenetic/FISH data have demonstrated 1p36 deletions in a relapsing familial clivus chordoma developed by a patient who has 2 daughters, respectively affected with childhood astrocytoma and clivus chordoma. Using an approach that combined the LOH (loss of heterozygosity) study of the father chordoma and the daughter astrocytoma and a segregation analysis from parents to sibs using 17 CA-repeats spanning 1p36.32-1p36.11, we mapped the cancer susceptibility locus in this family to the 1p36 region. The LOH and haplotype information was elaborated using a pairwise linkage analysis that gave a maximum lod score of 1.2. Additional LOH data relating to 6 sporadic chordomas allowed us to define an SRO (the smallest region of overlapping loss) of about 25 cM from D1S2845 (1p36.31) to D1S2728 (1p36.13). Our overall findings converge on mapping to 1p36 a tumor-suppressor gene involved in familial and sporadic chordoma.

First cytogenetic study of a recurrent familial chordoma of the clivus.

Two recurrences of a familial clivus chordoma, arisen from a patient who developed the primary tumor at age of 8 years, were investigated by cytogenetic and the fluorescence in situ hybridization (FISH) approach. Of the patient's 3 daughters, 2 developed, respectively, a clivus chordoma and an astrocytoma in infancy, a familial aggregation highly suggestive of a genetic background. After a 31-year hiatus, 2 tumor recurrences, developed over 17 months, were removed surgically. Both were hypo- or nearly diploid, and had a pronounced karyotypic heterogeneity with clonal and non-clonal rearrangements affecting several chromosomes. The same rearrangement, a dic(1;9)(p36.1;p21), was shared in both tumor specimens and, in 90% of the cells, chromosome 1p appeared to be involved in unbalanced translocations with different chromosomes, leading to variable losses of 1p. Previous cytogenetic data concerning chordoma are limited to 10 sporadic tumors with an abnormal karyotype; although no tumor-specific rearrangements have been identified, chromosome 1p appears to be involved frequently.

Glycoconjugate and adhesion molecule changes during the cell cycle in a human embryonic epithelial cell line.

The changes in the expression of glycoconjugates and adhesion molecules were studied by selective lectin binding and immunocytochemical reactions in a human embryonic epithelial cell line (EUE cells), synchronized in the cell phases. The results can be summarized as follows: most of the tested lectins display a more diffuse binding for the cytoplasm in G1 than S and G2 phases; in the S and particularly in G2 phases the cytoplasm glycoconjugates are arranged around the nucleus; cells in mitosis always show a strong binding towards all tested lectins. Cellular fibronectin and its receptor beta 1 integrin are well expressed in G1, but the strongest reaction is observed in the S phase. The immunoreactions for laminin and uvomorulin (L-CAM) are poorly positive in all cell cycle phases. The immunocytochemical reaction for heparan sulfate is positive, with a stronger reaction in S and G2 than G1; on the contrary a diffuse staining with the anti-dermatan sulfate proteoglycan antibody appears unchanged during the cell cycle.

Chromosomal instability in fibroblasts and mesenchymal tumors from 2 sibs with Rothmund-Thomson syndrome.

Rothmund-Thomson syndrome (RTS) is a rare autosomal recessive genodermatosis associated with increased risk of mesenchymal tumors. The putative gene has been provisionally assigned to chromosome 8. Using a cytogenetic-molecular approach, we studied lymphocytes, fibroblasts, osteosarcoma (OS) and malignant fibrous histiocytoma (MFH) from 2 affected fraternal twins, looking for constitutive markers of chromosome instability and tumor chromosomal changes which might reflect the common genetic background. The rate of spontaneous chromosome aberrations was not increased in lymphocytes. Conversely, karyotyping of primary fibroblasts from one sib evidenced chromosome breaks and both numerical and structural chromosome changes in 24% and 17% of the metaphases respectively. FISH of a 8q21.3 cosmid allowed us to detect trisomy of the target region on 7% of fibroblast nuclei from both sibs, 47% and 12% of OS and MFH cells. Pronounced chromosomal instability and clonal rearrangements leading to different chromosome-8 derivatives were detected in both tumors. CGH experiments showed multiple gains/losses, among which del(6q), also revealed by cytogenetics, and 7p gain were common, whereas 8q amplification was present only in OS. Chromosomal instability, observed in fibroblasts from the RTS patients studied, accounts for the increased risk of mesenchymal tumors in these patients.

Treatments with saline solutions and DNase I have different effects on DNA content and distribution in human and in mouse chromosomes.

The aim of this work was to re-examine, on a quantitative basis, the relationship between banding pattern after Giemsa staining and the amount (and distribution) of DNA along the length of the chromatid arms. To do this, we investigated by cytofluorometric methods the occurrence of possibly different extraction of chromosome DNA after some alternative G-banding procedure, i.e. treatment of chromosomes with saline solutions, or DNasi I digestion in situ. The G-banding procedure entailing trypsin pretreatment is known to be difficult to standardize; in the present investigation, it was also found that trypsin induced a massive, although quantitatively variable, extraction of DNA from fixed metaphase chromosomes. G-banding-like patterns may be obtained, by treating chromosomes preparations with saline solutions. Both PBS and Tris-HCl treatment for the times considered induced a G-banding-like pattern after Giemsa staining, regardless of the age of chromosome preparations; no banding was observed after staining DNA with PI, nor extraction of DNA was found to occur. DNase I digestion initially induced a G-banding in both human and mouse chromosomes after Giemsa staining, with concomitant extraction of DNA (but without apparent G-banding-like pattern after PI staining); after 30 min digestion, a C-banding-like pattern was observed after both Giemsa and PI staining. Exposure to PBS or Tris-HCl buffer at room temperature may therefore be recommended as a G-banding inducing treatment, since it allows the classification of single chromosomes after Giemsa staining, without determining significant displacement of genomic DNA, which can be submitted to further analysis in situ.

A stable marker chromosome with a cryptic centromere: evidence for centromeric sequences associated with an inverted duplication.

Centromere activation, an important mechanism in karyotype evolution, is occasionally observed in some human chromosome rearrangements. We report a possible occurrence of centromere activation in a marker chromosome containing an atypical centromere associated with an inverted duplication of the region 14q32 --> qter. The marker chromosome's reduced centromere lacks both the alpha and beta satellite sequences usually found at normal centromeres. In an attempt to identify the centromeric sequences, the marker chromosome was flow-sorted and amplified by a degenerate oligonucleotide primer polymerase chain reaction. Reverse chromosome painting experiments showed that the marker chromosome contains sequences that are unique to the distal region of chromosome 14, as well as a low copy number of (centromeric) sequences that are also highly represented in the centromeres of chromosomes 18 and 19. These data suggest the activation of a novel centromere in the 14q32 --> qter region, very likely consequent to the duplication of the region itself.

Hypertonic stress induces c-fos but not c-jun expression in the human embryonal EUE epithelial cell line.

Recent evidence has indicated a role for the two early response genes c-fos and c-jun in transcriptional regulation of genes acting in osmoregulation. On this basis we investigated their expression in response to hypertonic stress in the human embryonal EUE epithelial cell line. EUE cells have proven to be a useful tool for studying long-term in vitro adaptation to hypertonic stress. After culturing EUE cells in hypertonic medium a marked c-fos induction was observed, both at the mRNA and the protein level. Northern analysis of fos-mRNA showed a peak expression at 4 h, followed by a progressive decline till complete extinction at 8 h. Immunofluorescence analysis of FOS protein evidenced a similar, although slightly delayed kinetics of expression. Conversely, neither c-jun nor c-myc up-regulation could be detected. The treatment of EUE cells with cycloheximide led to superinduction of c-fos expression, (with high levels up to 12 h), and to a c-jun expression that was just detectable. Hypertonic stimulation of the transformed cell lines A549, MCF7 and JR induced both c-fos and c-jun only in JR cells. Hypertonic shock was also effective in inducing c-fos expression in fetal human diploid fibroblasts, although the response was earlier and more transient than in EUE cells. These findings indicate that c-fos is a primary response gene in hypertonic stress-activated cells, although the pattern and kinetics of its induction may differ according to the type of cell.

Cell cycle effects of hypertonic stress on various human cells in culture.

Long-term exposure to hypertonic (HT) culture media has been found to perturb the cell cycle and change gene expression in various animal cell types. A lower growth rate, with exit of cells from the cycling compartment has been observed previously in human transformed EUE cells. The aim of this study was to investigate if the kinetic changes after long-term HT stress, were typical of transformed cells or could be also found in primary cultures of normal cells. Human transformed cells from normal and neoplastic tissues, and normal human cells of epithelial and connective origin have been studied. After the incorporation of bromodeoxyuridine (BrdUrd), the frequency of S-phase cells was estimated by dual-parameter flow cytometry of DNA content versus BrdUrd immunolabelling; the total growth fraction was also estimated, after immunolabelling with an anti-PCNA antibody. We also investigated, by polyacrylamide gel electrophoresis, changes in the amount of a 35 kDa protein band, which increased in EUE cells grown in an HT medium, and which may be directly involved in cell resistance to hypertonicity. Lower BrdUrd labelling indices and higher frequencies of cells in the G0/1 range of DNA content were common features of all the cells in HT media, irrespective of their tissue of origin; other cycle phases may also be involved, depending on the cell type considered. The mechanisms by which cells cope with the HT environment could however differ, since only some cell types showed an increase of the 35 kDa stress protein found originally in HT EUE cells.

Nuclear phospholipids during the adaptation of human EUE cells to hypertonic stress.

The phospholipid component of interphase nuclei was analysed in EUE cells (an established cell line from embryonic human epithelium) grown in an isotonic culture medium and during the adaptation process to a hypertonic medium, using a highly specific ultracytochemical procedure, viz. labelling with the phospholipase A2 gold-complex. Within the nucleus, the phospholipids were localized in domains involved in different steps of the synthesis and processing of the RNA. These localizations did not vary at the two key steps of the adaptation process to hypertonic medium: short-term treatment (6 h) representing critical shock condition, and long-term growth (5 days) representing the adapted cells under survival conditions. On the contrary, deep changes of the labelling intensity of phospholipids at these sites occurred at the different times of hypertonic treatment and followed the same course as those observed in the ultramorphological patterns of transcription: the chromatin condensation, as evaluated by image analysis, the permanent nucleolar components, the interchromatin and the perichromatin granules. These data endorse the hypothesis that nuclear phospholipids could be involved in different steps of the transcriptional activity. They are indicative of the deep changes occurring in the EUE cells submitted to hypertonic stress.

Identification of the chromosome 14 origin of a C-negative marker associated with a 14q32 deletion by chromosome painting.

A constitutional chromosome 14 rearrangement was observed in a female with a psychodevelopmental disorder. Karyotype analysis using a variety of chromosome techniques, QFQ, GTG, CBG, Ag-NOR and DA-DAPI, showed a deletion of chromosome 14q32.1-qter region in association with a supernumerary marker chromosome. The marker, resembling a submetacentric, approximately half the size of a G group chromosome is C band and Ag-NOR negative. The heteromorphism of the satellites showed that the deleted chromosome 14 is paternal in origin. Chromosome painting using an Alu-PCR probe specific for the human chromosome 14 and fluorescent in situ hybridization (FISH) showed that the marker contains chromosome 14q32 sequences. It is likely that the marker was generated from the deleted chromosome 14 region through a complex rearrangement.

Aldose reductase is involved in long-term adaptation of EUE cells to hyperosmotic stress.

Aldose reductase has been shown to be expressed in large amount by human embryonic epithelial cells (EUE) in response to osmotic stress. This conclusion is the result of studies undertaken following the purification to homogeneity of two forms of a 35-kDa protein overexpressed in EUE cells grown in hypertonic saline culture medium as compared to EUE cells grown in isoosmotic medium. Amino-acid composition, molecular weight and partial internal amino-acid sequence showed that the above proteins are two different forms of aldose reductase. These findings were confirmed by the observation that aldose reductase activity increased about 150-fold in adapted cells and returned to basal levels in de-adapted cells.

Expression of cell cycle related proteins--proliferating cell nuclear antigen (PCNA) and statin--during adaptation and de-adaptation of EUE cells to a hypertonic medium.

EUE cells adapted to grow for long times in a hypertonic medium have a longer cell cycle than those growing in isotonic medium. To elucidate whether this lengthening involves specific cycle phases to differing extents, the expression of two cycle-related protein, PCNA and statin, was studied by dual parameter flow cytometry of indirect immunofluorescence protein labelling and DNA content. In isotonic medium, most cells, in all the cycle phases, were PCNA positive; in contrast, PCNA negative cells and statin positive cells were very few in number and only fell in the G0/1 range of DNA contents. In hypertonic medium, the frequency of PCNA positive cells was lower, and that of statin positive cells higher, than in isotonic medium, particularly in the G0/1 range of DNA contents: this suggests that a G0 block occurs under long-term hypertonic stress. Consistently, dual parameter flow cytometric measurement of BrdUrd immunofluorescence labelling and DNA content showed that fewer cells entered S phase in hypertonic medium and their progression through the S phase was slower; evidence was also found for the occurrence of a G2 block. These kinetics changes were fully reversible in isotonic medium, thus indicating the adaptive nature of the EUE response to hypertonicity.

A 33 kDa protein band is enhanced during long-term adaptation of EUE cells to a hypertonic medium.

A cell line derived from human embryonic epithelium (EUE cells) shows an enhanced expression of a 33 kDa protein when adapted to grow in a hypertonic medium containing 0.246 M NaCl (1.8 x the isotonic concentration). The maximum amount of this protein, followed by SDS-PAGE electrophoresis, was found after 4 days of adaptation; thereafter, the protein band remained fairly constant up to 30 days. When the cells were transferred back to a medium containing 0.137 M NaCl (isotonic medium), the protein pattern reverted to that of control cells. This protein is mainly localized in the cytosol, although a small part is associated with the 150,000 g pellet and needs detergents to be extracted. The molecular weight and the cellular location suggest a possible analogy with the so-called amphitropic proteins, that are known to interact with both the epidermal growth factor receptor and hydrophobic structures, such as the membrane phospholipids and the cytoskeletal components.

Cell kinetics of PHA-activated lymphocytes are slowed by prolonged hypertonic stress.

The effect of prolonged exposure to a hypertonic medium on human lymphocytes during mitogenic stimulation with phytohemagglutinin was investigated. The process of chromatin decondensation during the first 24 hrs stimulation (G0 to G1 transition) and the changes in kinetic parameters and the occurrence of chromosome aberrations from 48 hrs to 72 hrs of stimulation were studied. In HT medium, lymphocyte transition from G0 to G1 was slowed; there were fewer S-phase cells, after 48 hrs PHA stimulation, whereas after 72 hrs the resistant cells showed the same frequency of S-phase cells as the controls. The mitotic index was always smaller, and the frequency of G0/G1 cells larger. No significant increase in the frequencies of chromosome aberrations were found. These findings suggest that human peripheral lymphocytes can survive and grow in a hypertonic medium; chromosome damages, if not repaired, may be lethal, and only lymphocytes with normal karyotypes can survive for long times in the HT medium, although with modified kinetic characteristics.

Changes of gene expression during long term adaptation of human EUE cells to a hypertonic medium: electrophoretic protein patterns and DNase I digestion in situ.

The effects of long term (1 to 10 days) growth in a hypertonic medium have been studied in human EUE cells. Following polyacrylamide gel electrophoresis, a change in the protein pattern has been found, with the progressive enhancement, during adaptation, of a 33 kDa band. Experiments of DNA digestion in situ by DNase I showed that chromatin DNA of cells grown in a hypertonic medium is more available to the enzyme cleavage. These findings show that long term hypertonic stress is able to induce a change in gene expression in EUE cells.

Effect of hypertonic medium on human cell growth: III. Changes in cell kinetics of EUE cells.

The effects of hypertonicity on cell kinetics of EUE cells in culture have been investigated. After 4 days of growth in a hypertonic medium, the plating efficiency of EUE cells was reduced and cell growth was significantly slowed. Flow cytometric measurements of DNA content in synchronized cells, as well as flow cytometric determinations of DNA content and bromodeoxyuridine incorporation in asynchronous cells, also showed that the cell cycle is slowed in a hypertonic medium. In addition, the fraction of cycling cells is smaller and their progression through the S phase slower than in an isotonic medium.

Characterization of glycoconjugates in an embryonic human epithelial line and changes consequent to adaptation to a hyperosmotic medium.

Cell surface and cytoplasmic glycoconjugates were characterized in embryonic human explant cells (a transformed heteroploid line) cultured in iso-osmotic medium (0.137 M NaCl) and in hyperosmotic medium (0.274 M NaCl) for 10 days in order to study the changes induced in these compounds by hyperosmoticity. Cytochemical and ultracytochemical staining selective for glycoconjugates was carried out. The following results were obtained: (1) glycoproteins, glycosaminoglycans and glycolipids are present on the cell surface and in the cytoplasm of the explant cells; (2) lectin histochemistry combined with glycosidase digestion demonstrated the presence of the disaccharides fucose-N-acetylglucosamine and sialic acid-beta-galactose as terminal sequences; (3) histophotometric evaluation of lectin labelling showed a noticeable decrease in histochemical reactivity of adapted cells; (4) plasma membrane cell coat decreased in adapted cells, which was emphasized by ultracytochemical reactions and a rearrangement of glycolipids in the cytoplasm.

Effects of hypertonic conditions on cytoskeletal and adhesion structures of EUE cells.

The distribution of cytoskeletal structures has been studied by electron and immunofluorescence microscopy in human embryonic epithelial cells (EUE cells) exposed to a hypertonic medium containing 0.274 M NaCl. A first noticeable effect involved an increase of cell size. Microtubules, microfilaments and intermediate filaments were also considerably changed under these experimental conditions. The most marked effect was on intermediate filaments of the keratin type which formed very thick bundles around the nucleus and gave rise to an intracellular cagework which is likely i) to increase mechanical resistance and ii) to avoid cell collapse in conditions of hyperosmolarity. A remarkable increase in complexity of the microfilamentous network was also found: stress fibers became thicker and more densely arranged and vinculin-containing streaks at focal cell-substratum contacts increased in number and size; this indicated improved cellular adhesion. The phenotypic adaptation of EUE cells to conditions of hyperosmolarity is slowly reversible under defined experimental conditions.

Induction of 8-azaguanine resistant mutants in human cultured cells exposed to 31 MeV protons.

We report results on the induction of 8-azaguanine (8-AG)-resistant mutants in cultured human cells (EUE) exposed to 31 MeV protons. The spontaneous frequency of mutants was 5.6 +/- 0.7 x 10(-6) per viable cell. Gamma rays were taken as reference radiation. Expression times giving the highest frequency of mutants after 31 MeV protons and gamma irradiation were found to be about 10 days for both radiations. The dose-response relationship for mutant induction by protons, as determined at the optimal expression time, was compared to that obtained after gamma rays. The relative biological effectiveness (RBE) is 2.4 +/- 0.5, this value being higher than the RBE value determined for cell survival.